1. Field of the Invention
The present invention relates to a process for the regeneration of sulfuric acid containing hydrocarbons and water, such as sulfuric acid from a process wherein normal olefins are reacted with isoalkanes in the presence of sulfuric acid to produce alkylate product, to produce fresh sulfuric acid.
2. Related Information
In the petroleum refining industry, acid catalyzed alkylation of aliphatic hydrocarbons with olefinic hydrocarbons is a well known process. Alkylation is the reaction of a paraffin, usually isoparaffins, with an olefin in the presence of a strong acid which produces paraffins of higher octane number than the starting materials and which boil in the range of gasolines. In petroleum refining the reaction is generally the reaction of a C2 to C5 olefin with isobutane.
In refining alkylations, hydrofluoric or sulfuric acid catalysts are most widely used under low temperature conditions. Low temperature or cold acid processes are favored because side reactions are minimized. In the traditional process the reaction is carried out in a reactor where the hydrocarbon reactants are dispersed into a continuous acid phase.
Although this process has not been environmentally friendly and is hazardous to operate, no other process has been as efficient and it continues to be the major method of alkylation for octane enhancement throughout the world. In view of the fact that the cold acid process will continue to be the process of choice, various proposals have been made to improve and enhance the reaction and to some extent moderate the undesirable effects.
In the alkylation process the sulfuric acid catalyst becomes diluted with hydrocarbons and water which produces a sludge which must be disposed of. Typically the sludge is burned in a high temperature combustion zone to convert the acid to sulfur dioxide and the hydrocarbons to carbon oxides and water. The sulfur dioxide is then separated from the other combustion products and converted to sulfur trioxide in a vapor phase reaction over a vanadium-based catalyst. The sulfur trioxide is then converted to concentrated sulfuric by reaction with water in and absorber. One such process is disclosed in U.S. Pat. No. 3,907,979.
In a typical refinery or chemical application low cost spent acid disposal is not an option because of environmental regulations. Generally, the amount of spent acid produced is not sufficient to justify installation of an onsite conventional acid regeneration facility. The alternative is to ship the spent acid to a large scale sulfuric acid plant serving multiple spent acid generators and to receive pure acid in exchange. This alternative is not particularly attractive when compared to the cost of fresh acid.
It is an advantage of the present invention is that it provides an economically acceptable method for the onsite regeneration of spent sulfuric acid. It is another advantage that the present process provides an environmentally acceptable method for the onsite regeneration of spent sulfuric acid.